Adjustable wheel assembly

ABSTRACT

An improved wheel assembly comprises a caster fork, a caster wheel rotatably supported by the caster fork, and a caster swivel post defining an axis about which the caster fork rotates. The caster swivel post is being adapted to rotate about a pivot axis within a cylindrical housing. Alternatively, the wheel assembly has an adjustable axle for varying the camber angle of a wheel. The wheel assembly comprises a housing and an axle supported by the housing. The axle in turn rotatably supports a wheel. The axle is adapted to rotate about a pivot axis within a cylindrical housing.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 60/386,050, filed on Jun. 5, 2002.

BACKGROUND OF INVENTION

This invention relates in general to improvements in wheel assemblies ofthe type used with wheelchairs and other devices. More particularly,this invention relates to an improved caster wheel assembly having anadjustable caster swivel post for varying the angle of the caster swivelpost to ensure that the caster swivel post remains in a verticalorientation. Moreover, this invention relates to an improved rear wheelassembly having an adjustable axle for varying the camber angle of theaxle.

Caster wheel assemblies in general are well known in the art for usewith many different types of castered devices. Such caster wheelassemblies are commonly employed as the front wheels in a typicalwheelchair. Each caster wheel assembly typically includes a caster fork,which rotatably supports a relatively small diameter caster wheel, andwhich further includes a generally upright caster swivel post capturedby appropriate caster post bearings for rotation about a swivel axiswithin a fixed cylindrical housing. The fixed housing is adapted in turnfor mounting onto frame components of the wheelchair, or other castereddevice. Such caster wheel assemblies beneficially provide a high degreeof turning maneuverability.

The caster swivel post defines a vertically oriented axis about whichthe caster fork rotates. The caster post bearings are typically used toprovide a smooth, frictionless pivot. The caster wheel is rotatablysupported by the caster fork via a caster wheel axle, which is situatedrearward with respect to the caster swivel post. This ensures that thecaster wheel axle is always trailing the caster swivel post in thedirection of travel. The rearward offset distance of the caster wheelaxle with respect to the caster swivel post is commonly referred to asthe “rake”. The caster swivel post must be oriented vertically to ensurethat the caster wheel remains in contact with a supporting surface asthe caster fork pivots about the caster swivel post. This verticalorientation ensures that the caster wheel will not lift off thesupporting surface while turning.

Wheelchairs and other castered devices typically incorporate a number ofadjustments, including wheel height adjustment, wheel camber adjustment,and wheel size adjustment. Such adjustments are common with regard tothe rear wheels of the wheelchair to allow a wheelchair occupant tocustomize the wheelchair to his or her anthropometry or drivingconditions. When any of these adjustments are made, the angle of thecaster swivel post changes and must also be adjusted to ensure that thecaster swivel post remains vertical. Various means have been used toachieve caster swivel post angle adjustment, and are currently availableon the market. Such means are typically bulky, heavy, and cumbersome forthe user to adjust.

What is needed is an improved adjustable wheel assembly having a uniquemeans for providing adjustability and that is a very compact,lightweight, and easy for the user to adjust.

SUMMARY OF INVENTION

The present invention is directed toward an improved caster wheelassembly that meets all the foregoing needs. The caster wheel assemblycomprises a caster fork, a caster wheel rotatably supported by thecaster fork, and a caster stem defining an axis about which the casterfork rotates. The caster stem is being adapted to rotate about a pivotaxis within a cylindrical housing.

Moreover, this invention relates to an improved wheel assembly havingadjustable axle for varying the camber angle of a wheel. The wheelassembly comprises a housing and an axle supported by the housing. Theaxle, in turn, rotatably supports a wheel. The axle is adapted to rotateabout a pivot axis within a cylindrical housing.

Various objects and advantages of this invention will become apparent tothose skilled in the art from the following detailed description of thepreferred embodiment, when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a rear elevational view of an improved caster wheel assemblyaccording to the invention.

FIG. 2 is a cross-sectional view of the caster wheel assembly takenalong the lines 2-2 in FIG. 1.

FIG. 3 is an exploded front perspective view of the caster wheelassembly illustrated in FIGS. 1 and 2.

FIG. 4 is a reduced cross-sectional view of the caster wheel assemblyillustrated in FIG. 2, wherein the caster swivel post is adjustedforward with respect to the housing.

FIG. 5 is a reduced cross-sectional view of the caster wheel assemblyillustrated in FIG. 2, wherein the caster swivel post is adjustedrearward with respect to the housing.

FIG. 6 is a sectional view of an improved caster wheel assemblyaccording to another embodiment of the invention, wherein the casterswivel post is adjusted forward with respect to the housing.

FIG. 7 is a cross-sectional view of an improved caster wheel assemblyaccording to yet another embodiment of the invention, wherein the casterswivel post is adjusted rearward with respect to the housing.

FIG. 8 is a cross-sectional view of an improved caster wheel assemblyaccording to still another embodiment of the invention, wherein thecaster swivel post is adjusted forward with respect to the housing.

FIG. 9 is a cross-sectional view of an improved caster wheel assemblyaccording to another embodiment of the invention, wherein the casterswivel post is adjusted forward with respect to the housing.

FIG. 10 is a partial sectional view of an improved rear wheel assemblyaccording to the invention, wherein the axle sleeve is adjustable tochange the camber angle of the rear wheel.

DETAILED DESCRIPTION

Referring now to the drawings, there is illustrated in FIGS. 1-3 animproved caster wheel assembly 10 for use with many different types ofcastered devices (not shown). Caster wheel assemblies 10 according tothe invention are particularly useful as the front wheels in a typicalwheelchair (not shown). The caster wheel assembly 10 comprises a casterfork 12, which rotatably supports a relatively small diameter casterwheel 14, and which further includes a generally upright caster swivelpost 16 captured by the caster fork 12 by appropriate caster postbearings 18. The caster swivel post 16 is adapted to pivot about a pivotaxis A1 within a fixed cylindrical housing 20. The fixed housing 20 isadapted, in turn, for mounting onto frame components of the wheelchairor other castered device. The caster wheel assembly 10 provides a highdegree of turning maneuverability.

The caster swivel post 16 defines a vertically oriented axis about whichthe caster fork 12 rotates. This axis is coincident with the pivot axisA1 described about. The caster post bearings 18 are typically used toprovide a smooth, frictionless pivot. The caster wheel 14 is rotatablysupported by the caster fork 12 via a caster wheel axle 22, which issituated rearward, or toward the right when viewing FIG. 2, with respectto the caster swivel post 16. This ensures that the caster wheel axle 22is always trailing the caster swivel post 16 in the direction of travel,or toward the left when viewing FIG. 2. The caster swivel post 16 mustbe oriented vertically, or along the vertically oriented axis A1, toensure that the caster wheel 14 remains in contact with a supportingsurface (not shown) as the caster fork 12 pivots about the caster swivelpost 16. This vertical orientation ensures that the caster wheel 14 willnot lift off the supporting surface while turning.

Continuing with reference to FIGS. 2-3, the caster post bearings 18 arepreferably press fit within the caster fork 12 so that the caster postbearings 18 are concentric with respect to one another. Although twocaster post bearings 18 are shown, it should be appreciated by one ofordinary skill in the art of the invention that one or more caster postbearings or bushings may be suitable for carrying out the invention. Aninternal retaining ring 24 is provided for retaining and/or spacing thecaster post bearings 18 within the housing 20. A flat washer 26 isprovided within the internal retaining ring 24 and concentric with thecaster post bearings 18. The flat washer 26 is provided to maintain aspaced relation between the inner raceway 18 a of the caster postbearings 18.

The caster swivel post 16 is comprised of a stem bolt 28 having a shaft28 a having a lower end that mates with the inner raceway 18 a of thecaster post bearings 18. This allows the stem bolt 28 to rotate freelywith respect to the caster fork 12. An upper end of the shaft 28 a ofthe stem bolt 28 is threaded so as to thread into a pivot nut 30 withinthe housing 20. A pivot pin 32 passes through a cross-hole 30 a in thepivot nut 30, such that the pivot nut 30 can rotate about the pivot pin32, or about a pivot axis A2 defined by the pivot pin 32, whileremaining captive within the housing 20. The pivot pin 32 is held fixedwithin the housing 20. The pivot pin 32 may be comprised of, but is notlimited to, a bolt and nut, a dowel pin with one or more retainingrings, or a pin, such as the pivot pin 32 shown, with a central tappedhole 32 a held secure by two end screws 32 b.

A spline assembly, generally indicated at 34, resides between thehousing 20 and an upper one of the caster post bearings 18 within thecaster fork 12. The spline assembly 34 comprises an upper spline 36 thatis in fixed relation to the housing 20 and a lower spline 38 that is ina fixed relation to the caster fork 12. The upper and lower splines 36,38 can be integral with the corresponding housing 20 and caster fork 12or may be supported on separate members, as illustrated in the drawings.The upper spline 36 has a central slot 36 a therein while the lowerspline 38 has a central hole 38 a. The stem bolt 28 passes through thecentral hole 38 a in the lower spline 38 and the central slot 36 a inthe upper spline 36. When the stem bolt 28 is tightened into the pivotnut 30, teeth 38 b on the lower spline 38 lock into engagement with themating teeth 36 b on the upper spline 36, fixing the angular position ofthe caster swivel post 16 with respect to the frame of the wheelchair orcastered device (not shown). The center of curvature of the spline teeth36 b, 38 b is coincident with the pivot axis A2. The teeth 38 b, 36 b onthe lower and upper splines 38, 36 are preferably spaced two degreesapart along this radius of curvature, providing two-degree increments ofadjustment of the caster swivel post 16 with respect to the frame of thewheelchair or castered device. Because the pivot nut 30 can rotate aboutthe pivot axis A2, the pivot nut 30 remains aligned with the stem bolt28 over the range of angle adjustment of the caster swivel post 16. Thetotal range of adjustment of the caster swivel post 16 is limited by theclearance between the inner diameter 20 a of the housing 20 and theouter diameter 30 c of the pivot nut 30. According to a preferredembodiment of the invention, the inside diameter 20 a of the housing 20and outside diameter 30 b of the pivot post 30 are dimensioned to permita total adjustment range of about eight degrees forward and rearwardrelative to the housing 20, as shown in FIGS. 4 and 5. It should beappreciated by one of ordinary skill in the art of the invention thatthe caster wheel assembly 10 could be modified to provide coarser orfiner increments of adjustment, or a different range of adjustment,depending on the particular wheelchair or castered device application.

In operation, the stem bolt 28 can be loosened until the teeth 36 b onthe upper spline 36 and the teeth 38 b on the lower spline 38 separateenough to clear one another. The pivot nut 30 is then pivoted about thepivot axis A2 until the new desired angle is achieved. As clearlyillustrated in the drawings, the pivot nut 30 can be pivoted forwardrelative to the housing 20, or in a counter-clockwise direction whenviewing FIG. 4, or rearward relative to the housing 20, or in aclockwise direction when viewing FIG. 5. Ideally the angle is adjustedwith the stem bolt 28 as close to vertical when the wheelchair or othercastered device (not shown) is on a level supporting surface. The stembolt 28 is then tightened, causing the spline teeth 36 b, 38 b toengage, locking the caster swivel post 16 in a desired angular position.

The foregoing caster wheel assembly 10 is very compact and lightweight.This is achieved by placing the caster post bearings 18 in the casterfork 12, rather than in the housing 12. Placing the caster post bearings18 in this location allows the pivot assembly to occupy the housing 12.Because most of the angle adjustment components are internal to eitherthe housing 20 or the caster fork 12, the design is extremely compactand efficiently integrated into the wheelchair or other castered device.This produces a lightweight and low profile appearance.

It should be clearly understood that the present invention is notintended to be limited in scope to the preferred embodiment of theinvention described hereinabove. Several examples of alternativeembodiments of the invention are described hereinbelow.

As illustrated in FIG. 6, an upper end 40 a of a pivot stem bolt 40,instead of the pivot nut 30 illustrated above, can be supported withinthe housing 20 by the pivot pin 32. A stem nut 42 beneath of the casterpost bearings 18 on the lower end 40 b of the pivot stem bolt 40 servesto fix the spline assembly 34 between the caster post bearings 18 andthe housing 20 so as to retain the caster swivel post in a desiredangular position. The form and function of this embodiment is similar tothe embodiment described above.

Another embodiment of the invention is illustrated in FIG. 7. Thisembodiment of the invention comprises an angled wedge 44 between thecaster post bearings 18 and the housing 20. The wedge 44 functions toretain the caster swivel post 16 in a desired angular position. Thewedge 44 is secured in compression between the caster post bearings 18and an engagement key slot 46 a in a slotted member 46 fixed relative tothe housing 20. In order to adjust the angle of the caster swivel post16, the wedge 44 is removed from the assembly, and reoriented, orreplaced by a wedge, or series of wedges, having a different angle.Mating features on the engagement key slot 46 a and the wedge 44 ensurethat the wedge 44 is properly aligned when installed. These featuresallow the wedge 44 to be installed in two different positions byrotating the wedge 180 degrees about the caster swivel post 16. Itshould be appreciated by one of ordinary skill in the art of theinvention that the invention is not intended to be limited to the wedgeshown but may be carried out with any components with mating orinterlocking shapes, including but not limited to components havingcurved surfaces, hexentric shapes, curved acme threads, and curvedunified threads.

Yet another embodiment of the invention is illustrated in FIG. 8. Thisembodiment of the invention comprises a pivot nut 48 that resides withina housing 50, and which is allowed to rotate about a pivot axis A2within the housing 50. Two setscrews 52 are threaded into the pivot nut48 and bear against the housing 20 above and below the pivot axis A2 toprevent the pivot nut 48 from pivoting. The setscrews 52 are used toadjust and fix the angle of the pivot nut 48 with respect to thewheelchair or other castered device (not shown). The user can change theangle of the pivot nut 48 by adjusting setscrews 52 accordingly to fixthe angle of the pivot nut 48 with respect to the wheelchair or othercastered device. For example, to change the angle of the pivot nut 48 sothat the pivot nut 48 pivots rearward, or in a counterclockwisedirection when viewing FIG. 8, the user loosens the upper setscrew 52,or moves the upper setscrew 52 to the left when viewing FIG. 8, andtightens the lower setscrew 52, or moves the lower setscrew 52 to theright when viewing FIG. 8. The upper setscrew 52 resist movement of thepivot nut 48 in a counter-clockwise direction when viewing FIG. 8 andthe lower setscrew 52 resist movement of the pivot nut 48 in a clockwisedirection when viewing FIG. 8. It should be appreciated by one ofordinary skill in the art of the invention that the threaded setscrews52 may be threaded into a pivot stem bolt instead of the pivot nut 48shown.

Still another embodiment of the invention is illustrated in FIG. 9. Thisembodiment of the invention comprises a spline assembly 54 similar infunction to the spline assembly 34 of the preferred embodiment set forthabove, except that the pivot axis has been omitted. A spline insert 56fixed within the housing 58 has upper and a lower spline surfaces 56 a,56 b. These spline surfaces 56 a, 56 b are curved, having curvature thatis concentric with a virtual axis A3 about which the pivot stem bolt 60rotates when assuming different angular positions. The pivot stem bolt60 has a concave spline surface 60 a that engages the upper splineinsert surface 56 a. A spline washer 62 has an upper spline surface 62 athat engages the lower spline insert surface 56 b. A stem nut 64tightened beneath the caster post bearings 18 secures the angularposition of the pivot stem bolt 60.

It further should be appreciated that the present invention is notintended to be limited in scope to caster assemblies, as set forthabove, but could be applied to the rear wheels of a wheelchair (notshown) to allow for camber adjustment of the rear wheels. For example,there is illustrated in FIG. 10 a rear wheel assembly 66 comprising ahousing 68, such as the cylindrical camber tube shown, that is adaptedto be supported by the frame of a wheelchair (not shown). An axle sleeve70 is supported by to the camber tube 68. An axle 72 is in turn adaptedto be inserted into the axle sleeve 70 to rotatably support a relativelylarge diameter rear wheel 74 relative to the axle sleeve 70. The axle 72may include one or more spring balls 72 a that function to capture theaxle 72 in the axle sleeve 70. The rear wheel 74 provides a drivingforce for propelling the wheelchair.

The axle 72 defines an axis A4 about which the rear wheel 74 rotates.Wheel bearings 76 are used to permit the axle 72 to rotate smoothly andwithout significant friction. The wheel bearings 76 are preferably pressfit within the hub 74 a of the rear wheel 74 so that the wheel bearings76 are concentric with respect to one another. An inner end of the axlesleeve 70 is threaded so as to thread into a pivot nut 78 within thecamber tube 68. A pivot pin 80 passes through a cross-hole 78 a in thepivot nut 78, such that the pivot nut 78 can rotate about the pivot pin80, or about a pivot axis A5 defined by the pivot pin 80, whileremaining captive within the camber tube 68. The pivot pin 80 is heldfixed within the camber tube 68.

A spline assembly, generally indicated at 82, resides between the cambertube 68 and an axle sleeve nut 84 on an outer end of the axle sleeve 70.The spline assembly 82 comprises an inner spline 86, which is in fixedrelation to the camber tube 68, and an outer spline 88. The inner spline86 has a central slot 86 a therein while the outer spline 88 has acentral hole 88 a. The axle sleeve 70 passes through the central hole 88a in the outer spline 88 and the central slot 86 a in the inner spline86. When the axle sleeve nut 84 is tightened into the axle sleeve 70,teeth 88 b on the outer spline 88 lock into engagement with the matingteeth 86 b on the inner spline 86, fixing the angular position of theaxle sleeve 70 with respect to the frame of the wheelchair (not shown).

It should be clearly understood that the invention is not intended to belimited in scope to the rear wheel assembly described hereinabove andthat the invention can be practiced in numerous alternative embodimentsincluding, for example, embodiments similar to those set forth above andillustrated in FIGS. 6-9.

The principle and mode of operation of this invention have beenexplained and illustrated in its preferred embodiment. However, it mustbe understood that this invention may be practiced otherwise than asspecifically explained and illustrated without departing from its spiritor scope.

1. A wheelchair comprising: a frame having a front end and a rear end;and a caster wheel assembly mounted in relation to the frame, and casterwheel assembly comprising: a housing having a longitudinal axis; acaster fork; a caster wheel supported relative to the caster fork; acaster swivel post about which the caster fork pivots, the caster swivelpost being supported to pivot in forward and rearward directions about apivot axis that is within the housing and transverse to the longitudinalaxis of the housing; and a mechanism for holding the caster swivel postin a substantially fixed position.
 2. The caster wheel assemblyaccording to claim 1 further comprising an upper spline that is in fixedrelation to the housing and a lower spline that is adapted to lock intoengagement with the upper spline to fix the angular position of thecaster swivel post with respect to the housing.
 3. The caster wheelassembly according to claim 1 further comprising an angled wedge betweenthe caster fork and the housing to retain the caster swivel post in adesired angular position.
 4. The caster wheel assembly according toclaim 1 wherein the caster swivel post is supported to pivot about apivot axis that is perpendicular to the caster swivel post.
 5. Thecaster wheel assembly according to claim 1 further comprising matingsurfaces that lock together under tension in order to fix the angle ofthe caster swivel post with respect to the housing.
 6. A wheelchaircomprising: a frame having a front end and a rear end; and a casterwheel assembly mounted in relation to the frame, and caster wheelassembly comprising: a housing having a longitudinal axis; a casterswivel post that is supported to pivot in forward and rearwarddirections about a pivot axis within the housing and transverse to thelongitudinal axis of the housing; a mechanism for holding the casterswivel post in a substantially fixed position; a caster fork supportedfor rotation about the caster swivel post; and a caster wheel supportedfor rotation by the caster fork.
 7. The caster wheel assembly accordingto claim 6 further comprising an upper spline that is in fixed relationto the housing and a lower spline that is in a fixed relation to thecaster fork, the lower spline being adapted to lock into engagement withthe upper spline to fix the angular position of the caster swivel postwith respect to the housing.
 8. The caster wheel assembly according toclaim 6 further comprising an angled wedge between the caster fork andthe housing to retain the caster swivel post in a desired angularposition.
 9. The caster wheel assembly according to claim 6 wherein thepivot axis is perpendicular to the caster swivel post.
 10. The casterwheel assembly according to claim 6 further comprising mating surfacesthat lock together under tension in order to fix the angle of the casterswivel post with respect to the housing.
 11. A wheelchair comprising: aframe having a front end and a rear end; and a caster wheel assemblymounted in relation to the frame, and caster wheel assembly comprising:a housing; a caster swivel post supported within the housing for pivotalmovement in forward and rearward directions about a pivot axis withinthe housing and transverse to the longitudinal axis of the housing; amechanism for holding the caster swivel post in a substantially fixedposition; a caster fork supported relative to the caster swivel post;and a caster wheel rotatably supported by the caster fork.